From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755452AbaCCWpO (ORCPT ); Mon, 3 Mar 2014 17:45:14 -0500 Received: from mail-qa0-f54.google.com ([209.85.216.54]:33794 "EHLO mail-qa0-f54.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755005AbaCCWpJ (ORCPT ); Mon, 3 Mar 2014 17:45:09 -0500 Date: Mon, 3 Mar 2014 17:45:05 -0500 From: Tejun Heo To: Sasha Levin Cc: lizefan@huawei.com, containers@lists.linux-foundation.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] cgroup: missing rcu read lock around task_css_set Message-ID: <20140303224505.GE26523@mtj.dyndns.org> References: <1393729211-937-1-git-send-email-sasha.levin@oracle.com> <20140303223327.GB26523@mtj.dyndns.org> <5315057F.3030602@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5315057F.3030602@oracle.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Mar 03, 2014 at 05:43:11PM -0500, Sasha Levin wrote: > On 03/03/2014 05:33 PM, Tejun Heo wrote: > >On Sat, Mar 01, 2014 at 10:00:11PM -0500, Sasha Levin wrote: > >>rcu read lock should be held when calling and working with task_css_set. > >> > >>This patch also fixes a related lockdep warning. > > > >Hmmm... PF_EXITING should be visible at that point and cset can't > >change anymore. We prolly need to update lockdep annotation rather > >than adding spurious rcu locking around it. Against which branch is > >it? Can you please post the lockdep warning? > > I see it on -next. I think the right thing to do is using task_css_set_check() with PF_EXITING check and add comment explaining that cset can no longer change. Can you please write up a patch? Thanks. -- tejun